1. Field of the invention
This invention relates to a process for manufacture of an article having an embossed plastic sheet covering and an apparatus for suitably employable for performing said process.
2. Description of prior art
A composite material comprising a rigid core body and an embossed plastic sheet is employed in various industrial fields, such as interior parts of automobiles, furniture, decorated panel, and various decorative materials. The embossment is made to have an artificial design, a repeated pattern, a leather pattern and the like. Particularly, an embossed sheet having a leather feeling as well as leather pattern is widely employed.
The above-described composite material is generally prepared by covering a rigid core body such as a rigid plastic body, a foamed plastic body or a metal body with a flexible plastic sheet having an embossed surface. The coverage is generally given to one side of the body. However, in most cases, the coverage is extended to an edge or rim of other side (i.e, reverse side) of the core body. Such composite material is illustrated in FIGS. 1A and 1B in the attached drawings.
FIG. 1A is a perspective view of a typical composite material 1 comprising a plate core body 2 and an embossed plastic sheet coverage 2 which is viewed from the reverse side. FIG. 1B is a sectional view taken along X--X line of FIG. 1A.
The composite material 1 has been previously manufactured using an apparatus illustrated in FIG. 2A.
In FIG. 2A, the apparatus comprises a male mold 11 which is composed of a protruded portion 12 having a number of through-holes 13 and a vacuum chamber 14 having at its bottom an outlet of air 15 which is connected to a vacuum source (not shown). A space 16 is formed on the vacuum chamber 14 and around the protruded portion 12. In the manufacture of the composite material, a core body 2 having a number of through-holes 2d are placed on the top of the protruded portion 12 of the male mold 11. The core body 2 has an adhesive on its upper surface 2a and an edge (rim) 2b of its lower (reverse) surface. Above the core body 2, a heated flexible plastic sheet 3 having an embossed upper surface 3a and a lower surface 3b coated with an adhesive is kept by a set of clamps 17.
The heated flexible sheet 3 is then placed on the core body 2 by lowering the clamps 17 and further caused to adhere to the upper surface of the core body 2 by succtioning the vacuum chamber 14, as is shown in FIG. 2B. Sleeves of the plastic sheet 3 are pushed into the space 16 by means of a pushing plate (or rod) 18. By this operation, the sleeves of the plastic sheet are caused to adhere to the edges of the lower surface of the core body 2. Thus combined core body and plastic sheet is then released from the male mold 11 and the combined portion is recovered from the plastic sheet by cutting it at a line between its fixed portion and its free portion.
By the above process, a composite material in the form illustrated in FIGS. 1A and 1B is manufactured. However, it is frequently observed that the obtained composite material shows deformed face at its edge portion. In more detail, a sleeve 4 of the combined plastic sheet 3 which adheres to a side 2c and an edge of the reverse surface 2b of the core body 2 frequently has a decreased thickness. Further, an embossment 4a formed on a surface of the plastic sheet sleeve at the extended portion (i.e, the portion on the side face and the edge) frequently disappears. Furthermore, it is frequently observed that a front surface of the combined plastic sheet has plural concaved portions on the openings of the through-holes. The troubles such as decrease of thickness, disappearance of embossment, and formation of concaved portions on the embossed surface make quality and commercial value of the composite material low.
In order to manufacture a composite material free from the above-mentioned troublesome features, an improved process using an apparatus comprising a female mold in addition to the male mold was invented. The apparatus and a process using the apparatus are shown in FIGS. 3A and 3B.
In the process, a heated flexible plastic sheet 3 is placed within a depressed portion 5 of a female mold 21. The female mold 21 comprises a vacuum chamber 24 and the depressed portion 5 arranged thereon. The vacuum chamber 24 has an outlet 25 which is connected to a vacuum source (not shown). The depressed portion 5 comprises a porous bottom surface 22. The plastic sheet 3 has an adhesive on its upper side 3b. The plastic sheet 3 is pushed onto the porous bottom surface 22 of the depressed portion 5 by discharging an air from a space between the sheet and the bottom surface by operating the vacuum source. On the heated flexible plastic sheet 3, a core body 2 having a lower surface 2a, a upper surface 2b and a number of through-holes 2d is placed. Subsequently, a male mold 31 composed of a protruded portion 32 having a number of through-holes 33 and a vacuum chamber 34 having at its top an outlet of air 35 which is connected to a vacuum source (not shown) is placed on the core body 2. The vacuum chamber 34 of the male mold 21 is then made vacuum by operating the vacuum source, whereby an air present between the core body 2 and the bottom surface 22 of the depressed portion 5 of the female mold 21, around the side of the core body, and above the edge of the upper surface of the core body 2 is discharged through the through holes 33. By this procedure, the upper surface 3b of the plastic sheet 3 and the lower surface 2a of the core body 2 is combined by an adhesive and further the sleeve portion of the plastic sheet is caused to adhere to the side and upper edge of the core body. The male mold 31 which has the core body 2 covered with the plastic sheet 3 on the protruded portion 32 is released from the female mold 21. Subsequently, the flexible sheet 3 is cut at an inner area on the upper surface 2b of the core body 2 to separate the core body 2 covered with an embossed plastic sheet from the flexible sheet.
By the above process, a composite material in the form illustrated in FIGS. 1A and 1B is manufactured. The resulting composite material is almost free from the deformation of the plastic sheet. However, it is still frequently observed that a front surface of the combined plastic sheet has concaved portions on the openings of the through-holes. Further, only a small-sized portion of the plastic sheet can be caused to adhere to the edge of the reverse surface of the core body. In other words, the coverage at the edge portion of the core body is insufficiently short. The troubles such as the short coverage at the edge portion and the concaved portions formed on the embossed surface still make quality and commercial value of the composite material low.
Further known is a process employing a female mold and a manual operation. This process is described below by referring to FIGS. 4A and 4B.
In the process, a heated flexible plastic sheet 3 is placed within a depressed portion of a female mold 41. The female mold 21 comprises a vacuum chamber 44 and the depressed portion arranged thereon. The vacuum chamber 44 has an outlet 45 which is connected to a vacuum source (not shown). The depressed portion comprises a porous bottom surface 42. At the top of the female mold, eaves 43 (member inwardly protruded over the depressed portion) is arranged. The plastic sheet 3 is pushed onto the porous bottom surface 42 of the depressed portion by discharging an air from a space between the sheet and the bottom surface by operating the vacuum source. The plastic sheet is molded in a cup form and then cooled on the female mold. The molded sheet 3 is then released from the female mold, and unnecessary portion is cut off. In the molded piece of sheet is placed manually a core body 2 having an adhesive at its lower surface 2a to combine the molded piece 3 (covering material) and the core body 2. Thus, a composite material is prepared. This process is disadvantageous in that the manual operation is required. Further, it is not easy to combine the core body and the molded plastic sheet with satisfactory fitness.